Environmental Engineering Reference
In-Depth Information
2-in. (5.1-cm) AC on
4-in. (10.2-cm base course
6-in. (15.2-cm)± heave
Separation
Curb/
gutter
Buckling
Sandstone
Heave
Claystone
Sandstone
(a)
Cut pad
Heave
Heave
Claystone
Sandstone
Sandstone
Typical
12-ft (3.7-m)-
deep piers
(b)
Clayey "creep soil"
Original ground surface
Structure
Clay-rich
soils used
as fill
Shallow footings
Claystone/sandstone bedrock
Clayey "creep soil"
left in place
(c)
FIGURE 10.44
Problems of heave and creep in the interbedded claystones and sandstones at Menlo Park, California:
(a) typical pavement damage; (b) damage to houses on shallow piers; (c) conditions resulting in creep damage.
(From Meehan, R.L. et al.,
Proc. ASCE J. Geotech. Eng. Div.,
101, 1975. With permission.)
The problems:
Damage from heave to houses and street pavements had been severe, with
movements of the order of 4 to 6 in. The major problem was that of differential movements
because of the alternating surface exposure of the dipping beds of sandstone and claystone
as illustrated in Figure 10.44a and b. Claystone swelling where structures have been
placed in cuts typically occurs over several years following construction. It may not be
observed for 1 or 2 years, but generally continues to be active for 5 to 7 years after con-
struction. Slopes are unstable, even where gentle. In dry weather the heavy black clays
exhibit shrinkage cracks a few feet or so deep. During the winter rains, the cracks close
and the clay becomes subject to downhill creep at about 1/2 in. (1.2 cm) per year. Downhill
movement of fills has occurred, causing severe distress in structures located partly in cut
and partly on fill as shown in Figure 10.44c. Attempted and successful solutions are
described in
Section 10.6.4.
Other Rocks
Pyritic Shales
In Kansas City, the Missouri limestone has been quarried underground and the space left
from the operations has been used since 1955 for warehousing, manufacturing, office, and
